1. Field of the Invention
The present invention relates to a method of communication which is applicable to a base station or a terminal equipment of, for example, the cellular wireless telephone system as well as to the base station and the terminal equipment to which the method of communication is applied.
2. Description of the Related Art
In a mobile communication such as a wireless telephone system, a plurality of base stations are arranged at regular intervals to make a service area and the multiple access which makes a plurality of mobile stations (terminal equipments or a subscriber) linked is performed in each base station. In this case, a predetermined transmission frequency band is allocated before hand to the respective base stations and a plurality of transmission channels are set or provided within the transmission frequency band. When a demand for communication is issued from any of the terminal equipments and so on, one of these transmission channels is allocated to that terminal equipment and the terminal equipment uses the allocated transmission channel to make the communication started via the base station.
As the communication system in which the transmission channels are set in this manner, there are, for example, Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA), etc.
Describing briefly each of these systems, the communication system of FDMA is one in which a plurality of transmission channels are provided by dividing the transmission band prepared by a unit of frequency. The communication system of TDMA is one in which a transmission channel is divided by a predetermined time unit to form a plurality of time slots within a single transmission channel, each of the time slots being allocated to the terminal equipments to be linked. Therefore, it is possible to link the plurality of terminal equipment using the single transmission channel. The communication system of CDMA is one in which a specified code is allocated to each of the terminal equipments and a carrier having the same frequency is subjected to spectrum spread modulation by the code for transmitting it to the base station. The receiving side discriminates a signal transmitted from that terminal equipment using the same code which is synchronized.
Incidentally, in the wireless telephone system, by whichever system the transmission channel may be provided, the transmitting capacity which can be transmitted by a single transmission channel is determined and so it is impossible to alter the transmitting capacity depending on a class of data to be transmitted. Generally, in case of the wireless telephone system, the transmitting capacity of one transmission channel is set to be such a capacity as is able to transmit audio data for communication by telephone.
However, it is recently being put into practice to enable various data other than audio data to be transmitted by using a wireless terminal such as a portable telephone. If it is possible to transmit data of only a certain transmitting capacity on one transmission channel as described above, it will inconveniently take plenty of time to transmit a great deal of data for example. In order to overcome the inconvenience, it will be necessary to set a greater transmitting capacity as the transmitting capacity which one transmission channel can transmit. However, if the transmitting capacity of one channel is made greater, the wider frequency band width of one transmission channel will become necessary, so that the number of transmission channels which can be set within the transmission frequency band allocated to one base station will decrease. Moreover, when data of comparatively small amount such as audio data are transmitted, data amount transmitted through respective transmission channels becomes smaller than an amount which can be transmitted through that channel, which will result in an inconvenience that the transmission frequency band is not effectively utilized.